JP3916660B2 - Electronic conveyor power saving device with reusable controller - Google Patents

Abstract

An electrotransport system (50) includes a reusable controller (52) having a power source (60) and a separable disposable drug-containing unit (70). The controller (52) contains a switch (62) which disconnects the power source (60) from current drain when the controller (52) is uncoupled from the drug unit (70). A coupling means (74,66,105,72,64,104) physically and electrically connects together the controller (52) and the drug unit (70) such that the controller (52) provides electrical current to the drug unit (70) for electrotransport delivery of the drug to a body surface (eg, the skin) of a patient.

Description

Technical field
The present invention relates to an electrotransport drug delivery system having a transport unit for holding a drug and a control unit that operates with electric power, wherein each unit is connected by a mechanical coupler.
Background art
As used herein, the term “electrotransport” generally refers to the transport of a drug (eg, a drug) through a membrane such as, for example, skin, mucous membranes or nails. Transport is guided or assisted by applying an electrical potential. For example, an effective therapeutic agent is introduced into the human body's circulation by electrotransport delivery through the skin. Electrotransfer, a widely used electrotransport process (also called iontophoresis), involves the electrically induced transport of charged ions. Another type of electrotransport, electroosmosis, involves the flow of liquid under the influence of an electric field. In addition, this liquid contains the chemical | medical agent conveyed. Yet another type of electrotransport, electroporation, involves the formation of transient pores in biological membranes by the application of an electric field. The drug can be delivered passively (ie, without electrical assistance) or actively (ie, under the influence of an electrical potential) through the pores. However, in any given electrotransport, several of these processes occur to some degree simultaneously. Thus, the term “electrotransport cage” as used herein should be construed to be the broadest possible and thus the term is charged regardless of the specific mechanism that actually carries the drug. Or an electrically guided or enhanced delivery of at least one drug that is not tinged or mixed with tinged and non-tinged.
The electrotransport device uses at least two electrodes that are in electrical contact with some part of the skin, nails, mucous membranes or other surface of the body. One electrode, commonly referred to as the “donor” or “active” electrode, is the electrode that carries the drug into the body. The other electrode, typically referred to as the “counter” or “return” electrode, serves to close the electrical circuit through the body. For example, if the drug being delivered is positively charged, i.e. a cation, then the anode is the active or donor electrode and the cathode serves to complete the circuit. If the drug is negatively charged, that is, if it is an anion, the cathode is the donor electrode. Furthermore, both anodic and cathodic are considered donor electrodes if cation and anionic drug ions, or uncharged or neutral charge drugs, are carried.
In addition, electrotransport delivery systems typically require at least one reservoir or source of drug to be delivered, typically in the form of a solution or suspension. Examples of such donor reservoirs include bags or holes, permeable sponges or pads, and hydrophilic polymers or gel matrices. Such a donor reservoir is electrically connected to the anode or cathode and is located between the anode or cathode and the body surface and is a fixed or sustainable source of one or more drugs or agents. I will provide a. The electrotransport device also has a power source such as one or more batteries. Typically, one pole of the power supply is electrically connected to the donor electrode and the opposite pole is electrically connected to the counter electrode. In addition, some electrotransport devices have electrical controllers that control the current applied through the electrodes to limit drug delivery. In addition, passive flux control membranes, adhesives to maintain contact between the device and the body surface, insulating membranes, and impermeable support membranes are other optional components of the electrotransport device.
All electrotransport drug delivery devices use an electrical circuit to electrically connect a power source (eg, a battery) and electrodes. In a simple device, such as that disclosed in Ariura et al., U.S. Pat. No. 4,474,570, a "circuit" is simply a conductive wire used to connect the battery and electrodes. Other devices use a variety of electrical components to control the amplitude, polarity, timing, waveform shape, etc. of the current supplied by the power source. See, for example, McNichols et al. US Pat. No. 5,047,007.
To date, commercial transdermal electrotransport drug delivery devices (eg, Phoresor, sold by Iomed, Salt Lake City, Utah, and Empi, St. Paul, Minnesota) Duper Iontophoresis System sold by the company, Webster Sweat Inducer Model 3600 sold by Wescor, Logan, Utah, Generally, a desktop power supply unit and a pair of skin contact electrodes are used. The donor electrode includes a chemical solution, and the counter electrode includes a biocompatible electrolyte salt solution. A “satellite” electrode is contacted to the power supply unit by a long (eg, 1-2 meter) conductive wire or cable. Examples of desktop power units that use "satellite" electrode assemblies include: Jacobsen et al. U.S. Pat. No. 4,141,359 (see FIGS. 3 and 4), LaPrade U.S. Pat. No. 5006108 (see FIG. 9). And U.S. Pat. No. 5,254,081 to Maurer et al. (See FIGS. 1 and 2). The power supply unit in such a device has an electric control unit for adjusting the amount of current supplied through the electrodes. The “satellite” electrode is connected to the power supply unit by a long (eg 1-2 meter) conductive wire or cable. Wire connections face disconnection, limited patient movement, mobility issues, and are not comfortable. The distance at which the electrode and the power source can be separated by the wire connecting the power source and the electrode is limited to the length of the wire.
Recently, in order to extend the period, a small, fully equipped electrotransport delivery device has been proposed that is sometimes worn on the skin without standing out under clothes. The electrical components of such miniaturized electrotransport drug delivery devices are also desirably miniaturized, which can be integrated circuits (ie, microchips) or small printed circuits. Batteries, resistors, pulse generators, capacitors and other electrical components are electrically connected to form an electronic circuit for controlling the amplitude, polarity, timing, waveform shape, etc. of the current supplied from the power source . Such small, fully equipped electrotransport transport devices include, for example, Tapper US Pat. No. 5,224,927, Sibalis et al. US Pat. No. 5,224,928, and Haynes et al., US Pat. No. 5246418. Unfortunately, however, as the electrotransport transport device becomes smaller, the power source (eg, battery) that powers the device must also be reduced, so battery capacity and battery life are a design issue. It becomes.
In addition to miniaturization of electrotransport devices, recently they use electrotransport devices with reusable controllers introduced to be used in units for containing (incorporating) multiple drugs. It has been proposed. The drug-containing unit is simply disconnected from the controller when the drug is empty, and a new drug-containing unit is then connected to the controller. In this way, relatively expensive hardware components (eg, batteries, LEDs, circuit hardware, etc.) of the device can be built into the reusable controller, and relatively inexpensive donor and counter reservoirs. Can be incorporated into a disposable drug-containing unit, thereby reducing the overall cost of electrotransport drug delivery. An example of an electrotransport device with a reusable controller adapted to be removably connected to a drug containing unit is described in Sage Jr. Other U.S. Pat. No. 5,320,597, Sibalis U.S. Pat. No. 5,358,483, Cyvalis et al. U.S. Pat. No. 5,135,479 (FIG. 12), and Devance et al. U.K. Patent Application No. 2239803. .
Description of the invention
One feature of the present invention is to provide an electrotransport system, in which the power source in the reusable control unit is electrically disconnected from the current control circuit, which circuit includes Includes internal circuit path closed until ready for use.
The present invention relates to maintaining battery strength and extending battery life in an electrotransport device comprising a reusable electronic controller adapted for use with a plurality of single-use (eg, disposable) self-contained units. . After the medicine in the medicine unit is used up, the unit is disconnected from the controller and discarded, and then replaced with a new one. The controller includes a power source (eg, one or more batteries) and circuitry that controls the timing, frequency, magnitude, etc. of the current supplied to the device. The control circuit includes internal circuitry such as a timing circuit that contacts both poles of the battery through circuit paths other than the patient's body during operation of the device. A switch is provided to ensure that the battery is electrically isolated from the closed internal circuit until the device is operational. The switch is automatically closed by coupling a disposable self-contained unit to the reusable electronic controller. When the integrated drug unit is decoupled from the reusable controller, the switch is automatically reopened and the battery (s) are again electrically disconnected.
The present invention is suitable for use in any electrotransport device comprising a reusable controller and a single use / disposable drug unit, particularly from the time the device is manufactured to the time it is first used for a patient. It is suitable for preventing leakage of current during the storage period. The present invention is particularly suitable in electrotransport devices that are not used for extended periods (eg, overnight, holidays / weekends, etc.) once the controller is opened and used.
[Brief description of the drawings]
In the drawings, similar parts are denoted by the same reference numerals.
FIG. 1 is a perspective view of a separable electrotransport device according to the present invention.
FIG. 2 is a cross-sectional view of the apparatus shown in FIG. 1 taken along line 2-2 of FIG. 1, showing an uncoupled configuration of the controller and drug unit.
3 is a cross-sectional view of the apparatus shown in FIG. 1 taken along line 2-2 of FIG.
FIG. 4 is an electrical schematic diagram of a preferred embodiment of the present invention.
FIG. 5 is a cross-sectional view of another electrotransport device, showing a configuration in which the controller and the chemical unit are not coupled, and the chemical unit has a third stud 73.
FIG. 6 is a cross-sectional view of the apparatus shown in FIG. 5, showing a configuration in which a controller and a chemical unit are combined.
FIG. 7 is a cross-sectional view of another electrotransport device, showing a configuration where the controller and drug unit are not coupled, the controller having posts 312 and 314, and the drug unit having a conductive strip 316.
FIG. 8 is a cross-sectional view of the apparatus shown in FIG. 7, showing a configuration in which a controller and a chemical unit are combined.
Embodiment of the present invention
FIG. 1 is a perspective view of an electrotransport device 50 having a reusable electronic controller 52 configured to be coupled to and uncoupled from a drug containing unit 70. The controller 52 is reusable. That is, it is used with a plurality of drug units 70, eg, a series of identical and / or similar drug units 70. On the other hand, the drug unit 70 typically has a limited life and is discarded after use, i.e., when the built-in drug has been transported or emptied.
Referring to FIG. 2, a cross-sectional view of system 50 along line 2-2 of FIG. 1 is shown, where drug unit 70 is not coupled to controller 52. A housing 56 of the controller 52 includes a printed circuit (PC) board 58, a battery power source 60 including two button cell batteries connected in series for supplying power to the PC board 58, and the power source 60 and the PC board 58. And a switch 62 for performing connection and disconnection. PC board 58 is formed in a conventional manner and has patterned conductive traces for interconnecting the components on the board.
The drug unit 70 is configured to be removably coupled to the controller 52, with the upper portion of the drug unit 70 proximate and facing the lower portion of the controller 52. The upper portion of the assembly 70 (assembly) is provided with male portions of two snap-type connectors, which are studs 72 and 74 extending upward from the drug unit 70. The lower portion of the housing 56 is provided with two openings 64 and 66 arranged and dimensioned to receive the studs 72 and 74.
The chemical unit 70 includes a liquid non-permeable flexible insulating substrate 71 adhered or laminated (overlapped) to a foam member (foam member) 75 having indentations (wells) 77 and 79. The substrate 71 may be made of polyethylene foam or polyester. The foam member 75 may be made of a polyethylene foam layer of a predetermined thickness having indentations 77 and 79 made by a punching or cutting method known in the art. Recesses 77 and 79 each include a reservoir and optionally electrodes 81 and 82. Thus, the recess 77 includes a reservoir 76 and optionally an electrode 81, and the recess 79 includes a reservoir 78 and optionally an electrode 82. At least one of the reservoirs 76 and 78 (eg, reservoir 76) contains a therapeutic agent (eg, a drug) to be delivered. Accordingly, electrode 81 and reservoir 76 are considered to be a donor electrode assembly, and electrode 82 and reservoir 78 are considered to be a counter electrode assembly. Reservoirs 76 and 78 are typically formed from a hydrogel and are in contact with a body surface (eg, skin) of a patient (not shown) in use.
The reservoirs (reservoir) 76 and 78 are surrounded by the edge of the substrate 71 and separated from each other by the foam member 75. The bottom surface of the foam member (ie, the surface in contact with the patient) is preferably coated with a skin contact adhesive. Release liner 80 covers the body contacting surfaces of the two reservoirs 76 and 78 and the adhesive coated surface of foam member 75 before unit 70 is used. Release liner 80 is preferably a sheet of polyester coated with silicone. Release liner 80 is removed when unit 70 is applied to the skin of a patient (not shown).
The studs 72 and 74 are made of a conductive material (eg, silver, brass, stainless steel or other material, or a polymer coated with some material, eg, silver coated ABS). Thus, both studs 72 and 74 conduct current supplied by controller 52. Stud 72 makes conductive contact with electrode 81 and reservoir 76, and stud 74 makes conductive contact with electrode 82 and reservoir 78.
The housing 56 of the controller 52 has recesses 102 and 103 immediately next to the openings 64 and 66, respectively. Conductive and radially resilient spring retainers (retainers) 104 and 105 are configured to be received by the recesses 102 and 102 '. The spring retainers 104 and 105 are configured to releasably latch at their respective peripheral recesses when the studs 72 and 74 are inserted through the openings 64 and 66. Studs 72 and 74 are removably retained by individual spring retainers 104 and 105, thus removably connecting drug unit 70 to housing 56 of controller 52.
Conventional electronic connection means (eg, conductive wires, traces, or leaf springs (not shown)) electrically connect the spring retainers 104 and 105 to the individual conductive traces (not shown) at the bottom of the PC board 58. Connecting.
The switch 62 is attached to the bottom of the PC board 58. The switch 62 includes two terminals 112 and 114 that are welded or electrically connected to individual traces (not shown) of the PC board 58. One terminal 114 of switch 62 is electrically connected to one pole of battery power supply 60 and the other pole of battery power supply 60 is electrically connected to system ground 125. The terminal 112 of the other switch is connected to the input terminal 126 of the current control circuit 128.
The switch 62 may be a conventional metal leaf spring switch or a SKHUAB or SKHUAA type switch available from Alps Electric (USA) of San Jose, California. The switch 62 is designed so that (i) the switch remains in the open position when the drug unit 70 is not coupled to the controller 52 and (ii) closes when the drug unit 70 is coupled to the controller 52. Is not particularly important. The particular switch 62 shown in FIGS. 2 and 3 is a single pole single throw switch, having an actuating face 116 disposed substantially in parallel with the bottom surface of the controller 52, and a plunger 115 biased by a spring. including. The switch 62 is located at the bottom of the PC board 56 so that when the stud 72 is inserted into the opening 64, the actuation surface 116 and the opening 64 are essentially coaxially aligned with the stud 72. In FIG. 2, the plunger 115 is shown in the fully extended position, that is, when the medicine unit 70 is removed from the controller 52. When the stud 72 provides a pushing force against the working surface 116 while the drug unit 70 is coupled to the controller 52, the plunger 115 contracts against the force of the internal spring.
When the drug unit 70 is decoupled from the controller 52 and the spring of the plunger 115 is in the extended state, the switch terminals 112 and 114 are opened (ie, the switch 62 is opened). When the plunger 115 is contracted, that is, when the chemical unit 70 is connected to the controller 52 as shown in FIG. 3, the switch terminals 112 and 114 are electrically connected (that is, the switch 62 is closed).
The PC board 58 and the switch 62 connect the chemical unit 70 with the stud 72 at the same time (i) the plunger 115 contracts and electrically connects the terminals 112 and 114 of the switch 62 and (ii) the spring retainer 104. Mounted within housing 56 to mechanically couple to controller 52.
The switch terminals 112 and 114 are electrically connected in series with the power supply circuit of the PC board 58. Although the present invention is not limited to any current level, circuit, time, or drug delivery mode, an example of a timed power circuit (ie, applying electrotransport current to a patient for a predetermined period of time) As shown in FIG.
The control circuit 120 includes two output terminals 134 and 135 for supplying a control current, Ic, to the electrode assemblies 81, 76 and 82, 78. The controlled current Ic is applied to the patient's skin when the electrode assembly 70 and the controller housing 56 are attached together as described above and the reservoirs 76 and 78 are attached to the patient's skin or mucous membrane. The supply current, Ip, to the control circuit 128 is zero until the two switch terminals 112 and 114 are connected by closing the switch 62 (not shown in FIG. 4) by actuation of the plunger 115. Timing circuit 128 therefore provides zero current, Ic, to draw no quiescent current from power supply 60 until drug unit 70 is mechanically coupled to controller 52 and switch 62 is closed. To be suppressed. This ensures that the energy stored in the power supply 60 is stored until the controller 52 and drug unit 70 are coupled as described above.
Through conductive traces (not shown) made on the PC board 58 that make electrical contact with corresponding ones at the ends of the spring retainers 104 and 105, the two outputs 134 and 135 are the donor electrode assembly 81. And 76 and counter electrode assemblies 82 and 78, respectively, are connected through conductive segments.
The current Ic for supplying the therapeutic agent contained in the reservoir 76 flows from the output 134 through the spring retainer 104, the stud 82, the electrode 81 and the reservoir 76 into the patient (not shown).
In a compatible embodiment of the control circuit 120, another controlled waveform different from the continuous constant current waveform can be used. Multiple combinations of pulsed, sinusoidal, ramped and such various time-varying waveforms may be provided by a feedback control method if desired.
Reference is again made to FIGS. In use, the patient or physician selects the reusable controller 52 and the desired disposable electrode assembly 70. The controller 52 and the assembly 70 are stored in an inactive state for an indefinite period of time without leakage of current from the battery power source 60 because the switch 62 is normally open.
Studs 72 and 74 are aligned with and inserted into the respective openings 64 and 66 of housing 56. When inserted, the stud is guided by itself and makes conductive contact with the respective spring retainers 104 and 105. As the studs 72 and 74 are further inserted, the spring retainers 104 and 105 slide around the stud head until they engage the stud recess. At the same time, the head of stud 72 physically moves actuating plunger 115 and electrical contact between switch terminals 112 and 114 is made. In this way, terminals 112 and 114 complete the connection of power supply 60 in circuit 120. Engagement of the retainers 104 and 105 in the recesses of the studs 72 and 74 now completes the mechanical coupling of the housing 56 and the drug unit 70 to form a single unit. Optionally, the completion of the coupling between the medicine unit 70 and the controller 52 may be notified to the user by lighting the LED 158 in a predetermined blinking pattern after the switch 62 is closed. The combined device 50 is then placed on the patient's body and reservoirs 76 and 78 are in contact with the patient's body surface (eg, skin). Once the reservoirs 76 and 78 are connected to the patient's skin, the current Ic begins to flow through the electrode assemblies 81, 76 and 82, 78 and through the patient's body.
The controlled current Ic delivery continues until completion of the timed program in timing circuit 128, depletion of therapeutic agent in reservoir 76, or removal of system 50 from the patient's skin.
Completion of a predetermined time of therapeutic drug delivery or depletion of the disposable electrode assembly 70 may be indicated, for example, by flashing the LED 158.
The patient or medical technician then removes the studs 72 and 74 of the spent drug unit 70 from the openings 64 and 66 and the retainer springs 104 and 105 by pulling the drug unit 70 away from the housing 56. Removing the stud 72 from the opening 64 extends the plunger 115 again, thereby opening the switch 62 and disconnecting the power supply 60 from the power circuit 120. The remaining battery charge of the power supply 60 is saved by opening the power circuit 20. A replacement drug unit 70 is attached to the housing 56 and is attached to activate the switch 62 at a later time (eg, when performing another procedure on the same or another patient). When switch 62 is activated, switch terminals 112 and 114 are connected and power circuit 120 is reconnected, and the combined controller 52 and drug unit 70 are used for the patient as before and continue to deliver the therapeutic agent. To be ready to do.
Referring to FIGS. 5 and 6, an electrotransport device 150 comprising a reusable electronic controller 152 and a disposable drug unit 170 is shown. Unlike the device 50 shown in FIGS. 1-3, the reusable controller 152 has a third opening 68 adapted to receive the third stud 73 of the drug unit 170. At least the head of the stud 73 is made of a conductive material (for example, metal or a polymer coated with metal). The bottom of the circuit board 58 of the controller 152 includes a pair of spring terminals 212 and 214 that are open and functionally correspond to the terminals 112 and 114 of the controller 52. When the drug unit 170 is coupled to the controller 152, the stud 73 extends through the opening 68 and engages the spring terminals 212 and 214. Since the head of stud 73 is conductive, when stud 73 engages spring terminals 212 and 214, the circuit between terminals 212 and 214 is closed, thereby connecting power supply 60 to circuit 128.
Referring now to FIGS. 7 and 8, an electrotransport device 250 comprising a reusable electronic controller 252 and a disposable drug unit 270 is shown. Unlike the device 50 shown in FIGS. 1-3, the device 250 includes conductive posts 312 and 314 that extend through the bottom of the housing 56. The ends of posts 312 and 314 are brought into contact with conductive strips 316 on the top surface of substrate 71 when drug unit 270 is coupled to controller 252 as shown in FIG. Conductive posts 312 and 314 perform similar functions as terminals 112 and 114 of device 50. That is, when the controller 252 is not coupled to the drug unit 270, the circuit between the posts 312 and 314 is open, and thus the power supply 60 is electrically isolated from the circuit on the circuit board 58. When the drug unit 270 is coupled to the controller 252, the posts 312 and 314 engage the conductive strip 316, thereby closing the open circuit and connecting the power supply 60 to the circuit on the circuit board 58.
Like the device 50 shown in FIGS. 2 and 3, the devices 150 and 250 have mechanical switching means that isolate the power supply 60 from the closed loop timing circuit 128 inside the circuit board 58. However, with respect to mechanical switching means, the closed loop timing circuit 128 consumes a small amount of current even if the drug unit is not coupled to the controller. Thus, the mechanical switching means (i.e., switch 62, stud 73 and spring terminals 212 and 214, and the combination of conductive strip 316 and posts 312 and 314) remains until just before the device is used, i. The closed internal circuit 128 is prevented from being electrically connected to the power supply 60 until coupled to the controller. Those skilled in the art will appreciate that the switches shown in FIGS. 2-3 and 5-8 can be replaced by other known mechanical switches that do not draw quiescent current from the power supply 60 without departing from the spirit of the present invention. It will be easy to understand.
The device 50 shown in FIGS. 2 and 3 has a stud 72 that performs two functions, ie, electrically connects the electrode assemblies 81 and 76 to the circuitry of the circuit board 58, but the stud 72 also has a switch 62. The power supply 60 is connected to the circuit on the circuit board 58. However, this “two function” is not necessary, as is clearly shown in devices 150 and 250 in FIGS.
Although the foregoing detailed description has described one embodiment of an electrotransport system having a reusable power saving controller in accordance with the present invention, the above description is merely illustrative and the disclosed invention is described. It should be understood that it is not limiting. Within the scope and spirit of the present invention, housing shapes, dimensions and materials, PC boards, batteries, switches and conductive traces, attached and interconnected components, electrode assemblies, connectors and retention spring materials, types and It will be appreciated by those skilled in the art that it is possible to change the shape or to include or exclude various elements. That is, the present invention is limited only by the scope of the claims.

Claims (9)

An electrotransport system (50) for delivering a therapeutic agent across the surface of a patient's body, comprising:
a) a disposable assembly (70) having a pair of electrodes (81, 76 and 82, 78), at least one containing the therapeutic agent to be delivered and discarded after a single use;
b) a bipolar power supply (60) and a current control circuit (58) in electrical contact with both electrodes of the bipolar power supply (60) through a closed circuit path other than passing through the surface of the patient's body; A reusable controller (52) for providing to the electrode;
c) couplers (72, 64, 104) for electrically coupling and uncoupling the controller (52) and the assembly (70);
d) operatively connected to the coupler (64, 72, 104) and coupling the bipolar power supply (60) to the control circuit (58) by coupling the controller (52) and the assembly (70). And a switch (52) electrically disconnecting the bipolar power supply (60) from the control circuit (58) by disconnecting the controller (52) and the assembly (70). 62)
The controller (52) is coupled to the assembly (70) via the coupler (64, 72, 104), and thus is included in the controller (52) and the assembly (70). The controller ( 52 ) is kept separate from the therapeutic agent, and thus the controller ( 52 ) is separate from the disposable assembly (70) and is continuous with a plurality of disposable assemblies each containing a different therapeutic agent. An electrotransport system that can be reused by being combined together. The electrotransport system of claim 1, wherein the coupler comprises a conductive snap connector (72). The electrotransport system according to claim 1, wherein the coupler comprises a pair of conductive snap connectors (72, 74). The electrotransport system according to claim 1, wherein the bipolar power supply (60) comprises a battery. The electrotransport system according to claim 1, wherein the current control circuit (58) comprises a timing circuit (128) for controlling the length of supply time during which current is supplied to the electrodes (81, 82). An electrotransport system characterized by this. 2. The electrotransport system of claim 1, wherein when the controller (52) and the assembly (70) are coupled, the coupler (72) engages the switch (62) and the switch (62). 62) closing the electrotransport system. The electrotransport system of claim 1, wherein the switch (62) is a biased single pole single throw switch. The electrotransport system of claim 1, wherein the switch comprises a stud (73) that contacts a pair of spring terminals (212, 214). The electrotransport system according to claim 1, wherein the switch comprises a pair of posts (312, 314) and a conductive strip (316).

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